Meditating on the word is not optional if you want

"This Book of the Law shall not depart from your mouth, but you shall meditate in it day and night, that you may observe to do according to all that is written in it. For then you will make your way prosperous, and then you will have good success. Have I not commanded you? Be strong and of good courage; do not be afraid, nor be dismayed, for the LORD your God is with you wherever you go." Joshua 1:8-9

"I am the true vine, and My Father is the vinedresser. Every branch in Me that does not bear fruit He takes away; and every branch that bears fruit He prunes, that it may bear more fruit. You are already clean because of the word which I have spoken to you. Abide in Me, and I in you.

As the branch cannot bear fruit of itself, unless it abides in the vine, neither can you, unless you abide in Me. I am the vine, you are the branches. He who abides in Me, and I in him, bears much fruit; for without Me you can do nothing.

If anyone does not abide in Me, he is cast out as a branch and is withered; and they gather them and throw them into the fire, and they are burned. If you abide in Me, and My words abide in you, you will ask what you desire, and it shall be done for you. By this My Father is glorified, that you bear much fruit; so you will be My disciples." John 15:1-8 NKJV

God said it to Joshua and Jesus said it to His disciples.

Without it we can do nothing worth any eternal value. It keeps our minds clean and our hearts pure.